Recent content by JeSuisConf

Ok, it made it easier for me to think about but forget about what i said about cutting it in half. If x were greater than 36, then you would be outside the ellipse, but you want to say inside. Think of creating your rectangle using the variable x. If I set one corner at (x,0), then I can set...

You can quickly check your work using wolfram alpha... and according to it, (0,0) is one but your other answers are wrong.

Well, just cut in in half on the y-axis. The base of half your cuboid (... a rectangle or square in this case...) is just x. The height is 1296-x^2. We're looking on x=0 to 36, right? Well, almost. At what value of x is the height going to be at least 75% of the base? Then what's the area of...

Your explanation is super confusing. I suggest you not think of vectors as "from the origin." Just think of their direction. Think of points vs. vectors. I think you basically have it all correct but you're overcomplicating your problem.

Basically, you found the vector <2, -3, -9>, and that one is all good. You have everything correct except you want to use <-2, 5, 4> crossed with <2, -3, -9>, and not <4,3,7> crossed with <2, -3, 9>.

Yes, exactly. Because you took the cross product: ro X PoP1. But that would require that ro is parallel to the plane. It's not.

Ah, right my mistake. However, you did make this type of mistake, because (4,3,7) is not parallel to the plane either.

Well, by symmetry of the problem, no, it does not matter that there are k people (because the distribution of draws for any person is the same, so just imagine the first person.) As for the probability of exactly 1 marble, it is a rather ugly beast. There are m ways it can happen, and the...

Ok, (6,0,-2) is not a vector parallel to your plane. Here's how you do it: 1. Find any two points on that line 2. The vector between those two points is parallel to your plane 3. The vector between either point in the line and (6,0,-2) is also parallel to your plane Then you can take the cross...

I think you're on the right track but I am confused by what you are doing here. The way you typed the equation is unclear.

i think you confused a point in the plane and a vector in the plane. look carefully

Just look at how the standard basis vectors transform. Those are the columns of your rotation matrix. Also, for a change of coordinate systems, a rotation matrix need not exist (some changes are not rotations.)

Well, nobody here can do your research or give much help without knowing anything about it, but you might start by reading about http://en.wikipedia.org/wiki/Principal_component_analysis" .

Well if you can find the vector that joins the tip of P to the tip of Q, then you take two-thirds of that vector, add it to P, and you are two-thirds of the way to the tip of Q. Tto go from the tip of A to the tip of B, you need the vector B-A. Make sense yet?

Think about a vector that would join the tip of P to the tip of Q.